An EGR system, as is known, recirculates part of the exhaust gas back to the intake of an engine for reducing harmful nitrous oxide emissions. Fuel consumption and engine performance are affected by the recirculated exhaust gas flow. For example, engine performance may be affected by the temperature of the exhaust gas which is higher than that of the fresh air-fuel mixture introduced into the combustion chamber. The "hot" exhaust gas acts to heat up the combustible mixture thus facilitating the combustibility of the air-fuel mixture. As is known, the amount of exhaust gas returned is controlled by an EGR valve that is opened and closed by a control unit depending on operating conditions of the engine. To minimize exhaust gas emissions, it is important to accurately control the amount of exhaust gas recirculated according to engine operating conditions, such as, engine speed, temperature, altitude, exhaust gas pressure and temperature. Typically, with a cold start of the engine the EGR valve is initially closed to prevent recirculation, opened immediately after starting to recirculate exhaust gas to more quickly heat the engine and promote more complete combustion of fuel, and then closed when the engine warms up to operating temperature.
Prior couplers were a one-piece steel tube with an integral and slightly flexible bellows section. An orifice was disposed in the tube with only one pressure tap on one side of the orifice for a pressure sensor providing a signal used in controlling the EGR valve. The one-piece tube required close manufacturing and assembly tolerances for both the coupler and the engine to accurately locate the exhaust manifold and intake manifold mounting surface for the coupler. In service, the coupler became stressed, fatigued and cracked which resulted in expensive warranty, service and replacement costs for both manufacturers and consumers.